Brad Pitt Celebrates Birthday at Jennifer Aniston's Restaurant  12/28/06

Brad Pitt celebrated his 43rd birthday at ex-wife Jennifer Aniston's favorite West Hollywood restaurant where the two spent many nights together while they were married.

The star had been on the set of his new movie Ocean's Thirteen during the day and brought along pals George Clooney and Steven Soderbergh to help celebrate the occasion at Il Sole restaurant.

A source tells American publication US Weekly the dinner for 20 guests took place in the restaurant's private wine room and that, "It was a really mellow affair."

Pitt's girlfriend, Angelina Jolie, and their three children, Maddox, five, Zahara, two, and Shiloh, seven months, were not in attendance.

An eyewitness adds, "He looked tired but happy."